Input: atmel_mxt_ts - Make wait-after-reset peroid compatible with all chips

The delay before the chip can be accessed after reset varies between different
chips in maXTouch family. Waiting for 200ms and then monitoring the CHG (chip
is ready when the line is low) is guaranteed to work with all chips.

v4: Adjust delay depending on the family ID of the chip. Also add a readback
    of command register after backup is issued, to make sure we are not
proceeding
    too fast there.
v3: Add a check for NULL read_chg() function, and add the read_chg() to platform
    files using this driver (currently only mach-goni.c)
v2: At Dmitry's suggestion, add a timeout so we are not stuck looping
    endlessly in case the CHG is not going low.

Signed-off-by: Iiro Valkonen <iiro.valkonen@atmel.com>
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>
3 files changed